This invention relates to triggered vacuum gaps, and more specifically to a two stage triggered vacuum gap for use in high voltage applications where circuit interruption problems are likely to occur.
Two stage triggered vacuum gap devices are known which are operable during overload conditions to conduct overload current in an arc across an interelectrode gap, and to subsequently extinguish the arc. Greatly increased current conduction is obtained in such devices through a conductive plasma injected into the interelectrode gap during desired conducting periods, such as during overload conditions. Extensive studies have been conducted relating to the manner in which vacuum gaps are triggered to conduct current and to investigate the characteristics of the triggered vacuum gap. Two representative studies are discussed in "Triggered Vacuum Gaps," J. M. Lafferty, Proceedings of the IEEE, Volume 54, No. 1, Page 23, January, 1966, and "Low Voltage Firing Characteristics of a Triggered Vacuum Gap," George A. Farrall, IEEE Transactions on Electron Devices, Volume ED-13, No. 4, Page 432, April, 1966. U.S. Pat. No. 3,465,192 further discusses triggerable arc discharge devices and the manner in which plasma triggers may be constructed for use therein. A two stage triggered vacuum gap is disclosed in U.S. Pat. No. 3,798,484 having a plasma trigger mounted in an electrically floating midsection between the two stages in one case, and having the plasma trigger mounted in one of the end plates associated with one of the tube sections in the other case.
There is a need, therefore, for a two stage triggered vacuum gap device which is readily and reliably triggered by a plasma injection so that current conduction occurs simultaneously in each of the stages.